Search

The recent discovery of multiple viruses in ants, along with the widespread infection of their hosts across geographic ranges, provides an excellent opportunity to test whether viral prevalence in the field is associated with the complexity of social interactions in the ant population. In this study, we examined whether the association exists between the field prevalence of a virus and the intercolonial aggression of its ant host, using the yellow crazy ant (Anoplolepis gracilipes) and its natural viral pathogen (TR44839 virus) as a model system. We delimitated the colony boundary and composition of A. gracilipes in a total of 12 study sites in Japan (Okinawa), Taiwan, and Malaysia (Penang), through intercolonial aggression assay. The spatial distribution and prevalence level of the virus was then mapped for each site. The virus occurred at a high prevalence in the surveyed colonies of Okinawa and Taiwan (100% infection rate across all sites), whereas virus prevalence was variable (30%-100%) or none (0%) at the sites in Penang. Coincidentally, colonies in Okinawa and Taiwan displayed a weak intercolonial boundary, as aggression between colonies is generally low or moderate. Contrastingly, sites in Penang were found to harbor a high proportion of mutually aggressive colonies, a pattern potentially indicative of complex colony composition. Our statistical analyses further confirmed the observed correlation, implying that intercolonial interactions likely contribute as one of the effective facilitators of/barriers to virus prevalence in the field population of this ant species.

The longlegged ant Anoplolepis gracilipes (Smith) is a highly invasive tramp ant species known for its deleterious effects on native ecosystems. While tramp ants are associated with human activity, information on how different intensities of human activity affect their distribution is limited. This study investigated how anthropogenic activities affected the distribution of A. gracilipes in Penang, a tropical island in northern peninsular Malaysia. Three study sites (Youth Park, Sungai Ara, and Bukit Jambul/Relau) were selected, containing four sub-locations corresponding to different levels of human activity (low, moderate, high, and very high), determined by the average number of passersby observed over 30 min. Baited index cards were placed at each sub-location to evaluate ant abundance and distribution. The results demonstrated that A. gracilipes worker abundance was highest in areas of moderate human activity, as opposed to areas with low and higher human activity. The low abundance of A. gracilipes in comparatively undisturbed localities may be attributed to unsuitable microclimate, lack of propagule pressure, and diminished honeydew availability. In contrast, its exclusion from more urbanized localities could be explained by high interspecific competition with other tramp species and the absence of preferred nesting sites. [ABSTRACT FROM AUTHOR]

Ants are amongst the most successful invaders worldwide and can markedly modify invaded communities through biotic interactions. Invasive ants, for example, can compete with native pollinators for resources, act as legitimate pollinators, or disrupt plant-pollinator mutualistic interactions, thereby affecting native plant reproduction. Ecological restoration aims to mitigate the impact of invasive species and restore ecological communities and ecosystem functioning. Here we investigated the combined effects of two invasive ant species, the yellow crazy ant (Anoplolepis gracilipes) and white-footed ant (Technomyrmex albipes), on the pollination and reproduction of native plants in the context of a large-scale plant community restoration experiment. We conducted ant exclusion experiments and pollinator observations to obtain data on plant reproduction and pollination of four plant species. The experiments were conducted across eight granitic inselbergs on the island of Mahé, Seychelles, four of which are undergoing restoration since 2011 and four remained as invaded control sites (unrestored). Our findings indicate that native plants on Seychelles’ inselbergs relied primarily on flying flower visitors for pollination, considering that the contribution of ants to fruit set was generally small and substantially lower than that of flying pollinators. Moreover, while flying pollinators approached flowering plants irrespective of invasive ant presence, the number of probed flowers per visit was reduced, in both restored and unrestored communities. Therefore, native plant reproduction was negatively affected by the presence of invasive ants and this effect was similar in restored and unrestored plant communities. Our research suggests that invasive ants may contribute to changes in plant communities by deterring legitimate pollinators of native plants, an impact that is unlikely to be alleviated through early stages of ecological restoration.

BackgroundReproductive division of labor is one of the key features of social insects. Queens are adapted for reproduction while workers are adapted for foraging and colony maintenance. In many species, however, workers retain functional ovaries and can lay unfertilized male eggs or trophic eggs. Here we report for the first time on the occurrence of physogastric workers and apparent worker reproduction in the invasive yellow crazy ant Anoplolepis gracilipes (Fr. Smith). We further examined the reproductive potential and nutritional role of physogastric workers through multidisciplinary approaches including morphological characterization, laboratory manipulation, genetic analysis and behavioral observation.ResultsEgg production with two types of eggs, namely reproductive and trophic eggs, by physogastric workers was found. The reproductive egg was confirmed to be haploid and male-destined, suggesting that the workers produced males via arrhenotokous parthenogenesis as no spermatheca was discovered. Detailed observations suggested that larvae were mainly fed with trophic eggs. Along with consumption of trophic eggs by queens and other castes as part of their diet, the vital role of physogastric workers as "trophic specialist" is confirmed.ConclusionWe propose that adaptive advantages derived from worker reproduction for A. gracilipes may include 1) trophic eggs provisioned by physogastric workers likely assist colonies of A. gracilipes in overcoming unfavorable conditions such as paucity of food during critical founding stage; 2) worker-produced males are fertile and thus might offer an inclusive fitness advantage for the doomed orphaned colony.

Featured Application: This study offers fundamental insight for developing a model platform of artificial intelligence applicable for species distribution modeling, which has been currently emphasized for effective monitoring and control of invasive species. Recent advances in species distribution models (SDMs) associated with artificial intelligence (AI) and increased volumes of available data for model variables have allowed reliable evaluation of the potential distribution of any species. A reliable SDM requires suitable occurrence records and variables with optimal model structures. In this study, we developed three different machine learning-based SDMs [MaxEnt, random forest (RF), and multi-layer perceptron (MLP)] to predict the global potential distribution of two invasive ants under current and future climates. These SDMs showed that the potential distribution of Solenopsis invicta would be expanded by climatic change, whereas it would not significantly change for Anoplolepis gracilipes. The models were compared using model performance metrics, and the optimal model structure and spatial projection were selected. The MaxEnt exhibited high performance, while the MLP model exhibited low performance, with the largest variation by climate change. Random forest showed the smallest potential distribution area, but it was robust considering the number of occurrence records and changes in model variables. All the models showed reliable performance, but the difference in performance and projection size suggested that optimal model selection based on data availability, model variables, study objectives, or an ensemble approach was necessary to develop a comprehensive SDM to minimize modeling uncertainty. We expect that this study will help with the use of AI-based SDMs for the evaluation and risk assessment of invasive ant species. [ABSTRACT FROM AUTHOR]

Abstract Background Worker reproduction has an important influence on the social cohesion and efficiency of social insect colonies, but its role in the success of invasive ants has been neglected. We used observations of 233 captive colonies, laboratory experiments, and genetic analyses to investigate the conditions for worker reproduction in the invasive Anoplolepis gracilipes (yellow crazy ant) and its potential cost on interspecific defence. We determined the prevalence of worker production of males and whether it is triggered by queen absence; whether physogastric workers with enlarged abdomens are more likely to be reproductive, how normal workers and physogastric workers compare in their contributions to foraging and defence; and whether worker-produced males and males that could have been queen- or worker-produced differ in their size and heterozygosity. Results Sixty-six of our 233 captive colonies produced males, and in 25 of these, some males could only have been produced by workers. Colonies with more workers were more likely to produce males, especially for queenless colonies. The average number of days between the first appearance of eggs and adult males in our colonies was 54.1 ± 10.2 (mean ± SD, n = 20). In our laboratory experiment, queen removal triggered an increase in the proportion of physogastric workers. Physogastric workers were more likely to have yolky oocytes (37–54.9%) than normal workers (2–25.6%), which is an indicator of fertile or trophic egg production. Physogastric workers were less aggressive during interspecific aggression tests and foraged less than normal workers. The head width and wing length of worker-produced males were on average 4.0 and 4.3% greater respectively than those of males of undetermined source. Our microsatellite DNA analyses indicate that 5.5% of worker-produced males and 14.3% of males of undetermined source were heterozygous, which suggests the presence of diploid males and/or genetic mosaics in A. gracilipes. Conclusions Our experimental work provides crucial information on worker reproduction in A. gracilipes and its potential cost to colony defence. The ability of A. gracilipes workers to produce males in the absence of queens may also contribute to its success as an invasive species if intranidal mating can take place between virgin queens and worker-produced males.

Recent advances in species distribution models (SDMs) associated with artificial intelligence (AI) and increased volumes of available data for model variables have allowed reliable evaluation of the potential distribution of any species. A reliable SDM requires suitable occurrence records and variables with optimal model structures. In this study, we developed three different machine learning-based SDMs [MaxEnt, random forest (RF), and multi-layer perceptron (MLP)] to predict the global potential distribution of two invasive ants under current and future climates. These SDMs showed that the potential distribution of Solenopsis invicta would be expanded by climatic change, whereas it would not significantly change for Anoplolepis gracilipes. The models were compared using model performance metrics, and the optimal model structure and spatial projection were selected. The MaxEnt exhibited high performance, while the MLP model exhibited low performance, with the largest variation by climate change. Random forest showed the smallest potential distribution area, but it was robust considering the number of occurrence records and changes in model variables. All the models showed reliable performance, but the difference in performance and projection size suggested that optimal model selection based on data availability, model variables, study objectives, or an ensemble approach was necessary to develop a comprehensive SDM to minimize modeling uncertainty. We expect that this study will help with the use of AI-based SDMs for the evaluation and risk assessment of invasive ant species.

The yellow crazy ant, Anoplolepis gracilipes was first reported in Kenting National Park, Taiwan, in the 2000s, raising the concern of this invasive ant's potential effects on the native land crab populations. We investigated the distribution and abundance of A. gracilipes and its adverse effect on the land crab populations at four land crab hotspots within the park. Our survey results indicated that A. gracilipes was widespread and abundant at three of the study sites (Hsiangchiaowan, Shadao, and Natural Spring), while the distribution was much more confined at the fourth site (Houwan). Land crab populations experienced a notable decline at all the study sites except Houwan, indicating an inverse relationship between the population of land crabs and distribution/abundance of A. gracilipes. Combining the results of visual observations, the decline of land crab populations can be attributed, at least partially, to direct attacks by A. gracilipes on land crabs in their natural habitat and during the breeding migration season. Generalized additive model showed that worker abundance of this ant is associated with human disturbance levels, suggesting that anthropogenic disturbance may have contributed to the decline in land crab populations via promoting the abundance of A. gracilipes. [ABSTRACT FROM AUTHOR]

BACKGROUND: Insect growth regulators (IGRs) generally are considered to have safer eco-toxicological profiles than the more commonly used neurotoxins and metabolic inhibitors, and are extremely effective against several insect groups, including some invasive ant species. However, use of an IGR product in a large-scale eradication program for a widespread invasive ant (Anoploepis gracilipes; yellow crazy ant) was ineffective. We tested the IGR in question (active ingredient: (S)-methoprene) on A. gracilipes colonies in a laboratory environment to evaluate efficacy. RESULTS: We found that treatment with (S)-methoprene resulted in lower egg production with subsequently decreased numbers of larvae, pupae, and workers over the 135 days of the experiment. None of the treated colonies died, and the number of worker ants in treated colonies was 36% of that seen in control colonies 135 days post-treatment. Treated queen egg production was 39% lower than queens in control colonies, but we saw no effect of treatment on the internal physiology of dissected queens. Treatment had no effect on worker activity levels. CONCLUSION: Our results show that although (S)-methoprene treatment reduced production of larvae, pupae and workers in treated colonies, the magnitude of reduction was lower than might be expected considering the responses of other species against which this IGR has been tested. Our findings highlight a need for testing species-specific responses to IGR-based insecticides in a controlled environment, before broad-scale field applications that could result in suboptimal management of the target species. [ABSTRACT FROM AUTHOR]

Background: Worker reproduction has an important influence on the social cohesion and efficiency of social insect colonies, but its role in the success of invasive ants has been neglected. We used observations of 233 captive colonies, laboratory experiments, and genetic analyses to investigate the conditions for worker reproduction in the invasive Anoplolepis gracilipes (yellow crazy ant) and its potential cost on interspecific defence. We determined the prevalence of worker production of males and whether it is triggered by queen absence; whether physogastric workers with enlarged abdomens are more likely to be reproductive, how normal workers and physogastric workers compare in their contributions to foraging and defence; and whether worker-produced males and males that could have been queen- or worker-produced differ in their size and heterozygosity. Results: Sixty-six of our 233 captive colonies produced males, and in 25 of these, some males could only have been produced by workers. Colonies with more workers were more likely to produce males, especially for queenless colonies. The average number of days between the first appearance of eggs and adult males in our colonies was 54.1 ± 10.2 (mean ± SD, n = 20). In our laboratory experiment, queen removal triggered an increase in the proportion of physogastric workers. Physogastric workers were more likely to have yolky oocytes (37–54.9%) than normal workers (2–25.6%), which is an indicator of fertile or trophic egg production. Physogastric workers were less aggressive during interspecific aggression tests and foraged less than normal workers. The head width and wing length of worker-produced males were on average 4.0 and 4.3% greater respectively than those of males of undetermined source. Our microsatellite DNA analyses indicate that 5.5% of worker-produced males and 14.3% of males of undetermined source were heterozygous, which suggests the presence of diploid males and/or genetic mosaics in A. gracilipes. Conclusions: Our experimental work provides crucial information on worker reproduction in A. gracilipes and its potential cost to colony defence. The ability of A. gracilipes workers to produce males in the absence of queens may also contribute to its success as an invasive species if intranidal mating can take place between virgin queens and worker-produced males. [ABSTRACT FROM AUTHOR]

Sacred groves (SGs) of India are islets of forests providing ecosystem and spiritual services to man. Studies suggest that SGs are deteriorating on their quality due to urbanization, invasive species, land-use change, and religious modernization. We explored diversity, community, and abundance of overall and different functional groups of litter ants, including Anoplolepis gracilipes – an invasive ant – on paired SG-neighbouring home garden (HG) sites in rural and urban landscape to (a) assess the quality of SGs and (b) examine whether the variation in ant community of the two habitats was predicted by urbanization and abundance of A. gracilipes. We considered species and local contribution to β-diversity to identify species and sites crucial for conservation of sites. Abundance and richness of overall ants, proportional trap incidence of species, and abundance of A. gracilipes were similar on SG and HG, but species diversity and abundance of certain ant functional groups were higher on SG. Ant community of SG was different from HG, but was not affected by urbanization. A. gracilipes and rural SGs contributed the most to β diversity. A. gracilipes gave little pressure on native ant community. The study concludes that SGs, despite invaded by A. gracilipes, have potential for conserving biodiversity. [ABSTRACT FROM AUTHOR]

Hawaii has a single group of native bees belonging to the genus Hylaeus (Hymenoptera: Colletidae) and known collectively as Hawaiian yellow-faced bees. The majority of the 63 species have experienced significant declines in range and population. In 2016, seven species received federal protection under the Endangered Species Act of 1973. Competitors and predators, such as invasive bees, wasps and ants, are thought to be important drivers of range reductions and population declines, especially at lower elevations where more non-native species occur. We evaluated the effects of invasive ants on nesting Hylaeus anthracinus using artificial nest blocks that allowed us to track nest construction and development. The blocks were placed in pairs at 22 points encompassing three sites on the north and east sides of Oahu. One block in each pair was treated with a sticky barrier to prevent access by ants, while the other block remained untreated. From December 2015 to December 2016, we monitored 961 individual nests in the blocks. Seventy percent of nests in control blocks were invaded by ants. Nests in treated blocks were more likely to produce at least one adult than nests in untreated blocks (38% vs. 14%, respectively). In untreated blocks, ants were the most common cause of nest mortality followed by lack of development, displacement (primarily by the competitor Pachodynerus nasidens) and presumed pathogens. The invasive ant, Ochetellus glaber was the only observed nest predator, although the big-headed ant, Pheidole megacephala was also present. Hylaeus anthracinus inhabits coastal strand habitat which occurs in a narrow band just above the high tide line. Nests at one site were destroyed due to a high wave event, highlighting this species' vulnerability to sea level rise. Additionally, no adult bees or nests were observed at the points where yellow crazy ants, Anoplolepis gracilipes were established. An increased understanding of the factors limiting Hawaii's yellow-faced bees will provide information for future conservation efforts that may include landscape-scale ant control, habitat restoration and translocations. [ABSTRACT FROM AUTHOR]

Urbanization is a major threat to native biodiversity. Invasion of tramp species is a major consequence of urbanization, which might threaten native species. Ants are established robust ecosystem indicators. We assessed the changes of ant community in sacred groves (SGs) of urban and rural landscapes of south India between 2013 and 2019, and asked, 1) what is the effect of urbanization on ant community? 2) has the population of invasive ants, particularly Anoplolepis gracilipes – a globally notorious tramp species, changed in response to urbanization and year? 3) is species composition of ants in SGs different between landscapes and years? and 4) has the population of native ants or any ant functional groups responded with the population of invasive ants? The richness of overall species, native species, and invasive species was not affected by year or landscape, but the abundance was. In six years, the abundance of ants doubled, but due to A. gracilipes. A. gracilipes, previously restricted only in the urban SGs had established in rural SGs in six years. A significant turnover of native species was observed across years and with the population rise of A. gracilipes. While Generalist Myrmecines and Tropical Climate Specialists increased with the abundance of invasive ants, Cryptic Species decreased. We consider the stability maintained in the native species composition and richness in SGs, the aftermath of the conditions provided by SGs. However, the evident shift in the composition of native ants over the years point out how invasive ants affect the native species composition. [ABSTRACT FROM AUTHOR]

The current control measures used against common household ants in urban and agricultural settings include perimeter insecticide applications. These often have the potential to cause problems of poisoning non-target organisms, due to the insecticidal runoff and environmental contamination. A gel-baiting technique is the most effective tool to control ants with less insecticides released into the environment. In this study two commercial gel baits; the Boric acid (2.5% boric acid) and the Fipronil (0.01% fipronil) baits, were evaluated against laboratory made baits (lab baits). The lab baits, consisted of: 1.5% boric + fructose (F1.5), 1.5% boric acid + fructose + molasses (M1.5), 3% boric acid + fructose (F3), and 3% boric + fructose + molasses (M3) were evaluated based on preference and mortality rates of the common household ant species: the Asian needle ant, Monomorium chinensis, Santschi, and the Yellow crazy ant, Anoplolepis gracilipes, Smith, under laboratory conditions. An inconsistent preference was observed between species and different baits; however, the fipronil bait and the lab bait M3, were preferred more by both ant species compared to the other baits tested. Lab bait M3 also had a faster killing speed than the boric acid bait and the lab bait F3.Based on the results it was concluded that lab bait M3 was a more efficient ant bait and is a potential alternative control measure to the current commercial baits.

Abstract Background Reproductive division of labor is one of the key features of social insects. Queens are adapted for reproduction while workers are adapted for foraging and colony maintenance. In many species, however, workers retain functional ovaries and can lay unfertilized male eggs or trophic eggs. Here we report for the first time on the occurrence of physogastric workers and apparent worker reproduction in the invasive yellow crazy ant Anoplolepis gracilipes (Fr. Smith). We further examined the reproductive potential and nutritional role of physogastric workers through multidisciplinary approaches including morphological characterization, laboratory manipulation, genetic analysis and behavioral observation. Results Egg production with two types of eggs, namely reproductive and trophic eggs, by physogastric workers was found. The reproductive egg was confirmed to be haploid and male-destined, suggesting that the workers produced males via arrhenotokous parthenogenesis as no spermatheca was discovered. Detailed observations suggested that larvae were mainly fed with trophic eggs. Along with consumption of trophic eggs by queens and other castes as part of their diet, the vital role of physogastric workers as “trophic specialist” is confirmed. Conclusion We propose that adaptive advantages derived from worker reproduction for A. gracilipes may include 1) trophic eggs provisioned by physogastric workers likely assist colonies of A. gracilipes in overcoming unfavorable conditions such as paucity of food during critical founding stage; 2) worker-produced males are fertile and thus might offer an inclusive fitness advantage for the doomed orphaned colony.

BACKGROUND: Recent research on multiple invasive ant species has revealed the importance of carbohydrates for achieving high activity levels and outcompeting native ants. However, comparatively little is known about the role of diet and macronutrient preferences for uptake of insecticidal baits used to control invasive ants. We tested whether diet affected yellow crazy ant (Anoplolepis gracilipes Fr Smith) survival and behavior, and whether bait preference would be complementary to past diet. RESULTS: We found that colonies fed only crickets for 28 days had fewer live workers and queens, and less brood per live queen than colonies fed crickets + honeydew but did not differ significantly from colonies fed only honeydew. Colonies that had been fed only crickets were more active (as assessed by interaction with a novel object), retrieved 16–17 times more bait per worker overall, and consumed more of the six bait types than cricket + honeydew and honeydew‐only fed colonies. However, prior diet did not affect bait choice. The two highest sugar bait formulations combined accounted for most of the bait consumed across all treatments (cricket‐only 74.8% ± 28.1; cricket + honeydew 69.2% ± 12.4; honeydew‐only 62.5% ± 30.4). CONCLUSION: Yellow crazy ant colonies fare better without protein than without carbohydrates. Yellow crazy ants ate the most bait when fed only crickets but did not choose baits complementary to their previous diet. Baits in a sugar‐rich carrier may be most effective for the control of yellow crazy ants, regardless of the relative availability of macronutrients. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

We obtained 14,140 interception records of ants arriving in Australia between 1986 and 2010 to examine taxonomic and biogeographic patterns of invasion. We also evaluated how trade and transport data influenced interception rates, the identity of species being transported, the commerce most associated with the transport of ants, and which countries are the primary sources for ants arriving in Australia. The majority of ant interceptions, accounting for 48% of interceptions, were from Asia and Oceania. The top commodities associated with ant interceptions were: (1) Live trees, plants, cut flowers; (2) Wood and wood products; (3) Edible vegetables; and (4) Edible fruit and nuts. The best fitting model for predicting ant interceptions included volumes for these four commodities, as well as total trade value, transport volume, and geographic distance (with increased distance decreasing predicted ant interceptions). Intercepted ants identified to species consisted of a combination of species native to Australia, introduced species already established in Australia, and species not yet known to be established. 82% of interceptions identified to species level were of species already known to be established in Australia with Paratrechina longicornis having the most records. These data provide key biogeographic insight into the overlooked transport stage of the invasion process. Given the difficult nature of eradication, once an ant species is firmly established, focusing on early detection and quarantine is key for reducing the establishment of new invasions. [ABSTRACT FROM AUTHOR]

Development and reproduction of the hymenopteran parasitoid Tachardiaephagus somervilli Mahdihassan (Chalcidoidea: Encyrtidae) were studied in its native range in Malaysia as part of a classical biological control program on Christmas Island (Indian Ocean). Tachardiaephagus somervilli was reared in the laboratory on its target host, the yellow lac scale, Tachardina aurantiaca Cockerell (Coccoidea: Kerriidae). The developmental time, survival, and sex ratio of F1 offspring from two different sources of F0 adults (field-collected F0 adults [='wild-caught'] and F0 adults that emerged from parasitized hosts in the laboratory [='laboratory-emerged']) were compared. Sources of F0 adults did not affect the developmental time of either male or female offspring, which ranged from 23 to 25 days. Furthermore, per capita fecundity of laboratory-emerged F0 females was three times greater than wild-caught F0 females. The number of emerged F1 adults was positively related to host size. Tachardiaephagus somervilli has a short generation time relative to its female Tachardina hosts (~23 vs ~90 days), high fecundity (~16 emerged offspring per laboratory-emerged female) and can potentially complete 12–15 generations per year. This rearing protocol produced sufficient quantities of adult T. somervilli for the export and successful introduction to Christmas Island (Indian Ocean) for the biological control of invasive T. aurantiaca , with near 100% survival rates for both sexes during transit. Unlabelled Image • An encyrtid wasp was used as a biological control agent of the yellow lac scale. • Lab-emerged adults produced more offspring and lived longer than wild-caught adults. • Number of wasp offspring produced was positively related to lac scale size. • This parasitoid can yield 12–15 generations annually relative to 3–4 for its host. • Wasp export from Malaysia and introduction on Christmas Island was successful. [ABSTRACT FROM AUTHOR]

For conservation ecologists, the justification for restoration that involves the removal of invasive species is often made on the perception of impacts on biodiversity. However, invasive species control decisions can also be driven by the perceived direct impacts on people. Our case study reports on the ecological and human perspectives that drove the decision to control yellow crazy ants in Atafu, Tokelau. We surveyed the effects of yellow crazy ants at varying abundance on attitudes of people, diversity of ant communities, and white tern nesting behaviour in Atafu. Direct effects of yellow crazy ants on people included complaints that they 'ruined the garden', ate the 'food for pigs that is kept outside', and residents in areas with high ant infestations 'can't sleep outside anymore'. Yellow crazy ant abundance was positively correlated with both negative impacts on common ant species and the concern people expressed over the effects of the ant on their lives, but was not associated with differences in ant species richness or invertebrate diversity. We also found that yellow crazy ant abundance was negatively associated with the reproductive output of white terns. In addition, we found that people and white terns were more sensitive than ant communities to the effects of yellow crazy ants when the ants were at lower abundance. Based on our surveys of impacts on the villagers and biodiversity values on Atafu, the decision was made to embark on a control program, which was predicted to benefit both people and the environment. We report on the factors influencing the decision to control yellow crazy ants in Atafu, Tokelau. A combination of biodiversity impact surveys, measures of abundance of the ant invader, and surveys of peoples' opinions all supported the benefit of undertaking control. [ABSTRACT FROM AUTHOR]

Anoplolepis gracilipes is one of the six most widespread and pestiferous invasive ant species. Populations of this invader in Arnhem Land, Australia have been observed to decline, but the reasons behind these declines are not known. We investigated if there is evidence of a pathogen that could be responsible for killing ant queens or affecting their reproductive output. We measured queen number per nest, fecundity and fat content of queens from A. gracilipes populations in various stages of decline or expansion. We found no significant difference in any of these variables among populations. However, 23% of queens were found to have melanized nodules, a cellular immune response, in their ovaries and fat bodies. The melanized nodules found in dissected queens are highly likely to indicate the presence of pathogens or parasites capable of infecting A. gracilipes. Queens with nodules had significantly fewer oocytes in their ovaries, but nodule presence was not associated with low ant population abundances. Although the microorganism responsible for the nodules is as yet unidentified, this is the first evidence of the presence of a pathogenic microorganism in the invasive ant A. gracilipes that may be affecting reproduction. [ABSTRACT FROM AUTHOR]

A survey of the butterflies of Christmas Island, Indian Ocean, in March 2017 identified 23 of the 29 species recorded for the island. These include the first published records for Petrelaea tombugensis (Röber) (Lycaenidae), Badamia exclamationis (Fabricius), Hasora chromus (Cramer) and Borbo cinnara (Wallace) (Hesperiidae), all first taken in 2003 by Ian Knight and still present. Abundance, distribution and larval food plants for each butterfly species are discussed. Rainforests that cover most of the island contained the greatest diversity while the unrehabilitated mined areas had few butterflies. The presence of now common species such as Papilio memnon memnon Linnaeus, Appias olferna Swinhoe, Eurema blanda blanda Boisduval, Euchrysops cnejus cnejus (Fabricius) and Zizina otis (Fabricius), which were unrecorded prior to 1985, suggests that these species are recent arrivals. The life history of Papilio memnon memnon on Christmas Island is illustrated. Observations on yellow crazy ant (Anoplolepis gracilipes (Smith)) interactions with some species are recorded. [ABSTRACT FROM AUTHOR]

Host range estimation using historical records and field-based host specificity tests was performed with Tachardiaephagus somervilli , an encyrtid parasitoid selected for the biological control of the invasive lac scale Tachardina aurantiaca on Christmas Island, Indian Ocean. T. aurantiaca is tended by the invasive ant Anoplolepis gracilipes and its honeydew supply is implicated in formation of ant supercolonies that threaten native biodiversity and disrupt ecosystem processes in island forest. Historical data indicated that T. somervilli and other Tachardiaephagus spp. have narrow host ranges restricted to lac scales (Kerriidae). Furthermore, none of the 40 encyrtid species known to parasitize lac scales has a host range extending beyond the Coccoidea, and no encyrtid species is known that bridges the phylogenetic distance between their kerriid hosts and the families of any endemic Hemiptera found on Christmas Island. No-choice host specificity tests conducted in the field in the native range of Tachardina aurantiaca showed that none of the eight test species (Coccoidea) were parasitized by T. somervilli . These results predict that release of T. somervilli on Christmas Island will have negligible risks of non-target impacts. More broadly, host-specificity testing in the native region should play a greater role in assessment of potential biological control agents. [ABSTRACT FROM AUTHOR]

Ants are abundant in natural and managed tropical ecosystems and can have an impact on herbivorous arthropods, as well as plant pathogens. Although it has been shown for plants that the diversity of communities can result in improved ecosystem functioning, it remains uncertain how the species richness of ants affects multiple ecosystem services and disservices., In the present study, we used experimentally enhanced natural gradients in ant species richness on 100 cacao trees in a plantation aiming to analyze the effect of ant species identity and species richness on predation pressure and the incidence of cacao pod borer ( CPB), as well as the spread of black pod disease ( BPD)., Ant species richness did not significantly improve predation of experimentally exposed insects, and was not associated with a reduction in the incidence of CPB. However, the incidence of BPD was higher in ant species rich trees, presumably because more ant species were pathogen vectors. The identity of the dominant ant species affected the incidence of CPB and BPD, as well as predation pressure., Although both ant species richness and identity affected ecosystem services and disservices delivered by the ant community, the results of the present study suggest that the identity of dominant ants is the main driver for ecosystem services in these systems. [ABSTRACT FROM AUTHOR]

Yellow crazy ants ( Anoplolepis gracilipes) are a significant threat to biodiversity due to a rapidly expanding range and the potential to disrupt ecosystem interactions at multiple trophic levels. Extirpation of ground-nesting seabirds subsequent to yellow crazy ant invasion has been reported anecdotally. Yellow crazy ant control is difficult and resulting positive effects on nesting seabirds is undocumented. We report the effects of ant invasion and subsequent control on burrow-nesting seabirds following the invasion of more than half of a 1.25-ha wedge-tailed shearwater ( Ardenna pacifica) colony located on eastern O'ahu. The number of active seabird burrows in invaded areas dropped from 125 in 2006 to 6 in 2010, with no corresponding decline in active burrows in adjacent, uninvaded areas. Ant control efforts in 2011 reduced ant densities by more than 97% and resulted in a substantial increase in active burrows (43 in 2011). In invaded areas, burrows appeared to be abandoned by adults prior to egg-laying. Chicks surviving in invaded areas exhibited mild to severe developmental abnormalities, and overall had shorter culmens, tarsi and wingchords, smaller eye diameters, and lower weights than chicks outside invaded areas. We conclude that yellow crazy ants constitute a significant, and likely underestimated, risk to ground-nesting seabirds. Loss of seabird nesting colonies can have significant effects on nutrient inputs, and can bring about shifts in plant communities and faunal composition. Range expansion of yellow crazy ants is expected and ant/seabird interactions are likely to increase. [ABSTRACT FROM AUTHOR]

Sacred groves may contain remnants of pristine and primary forests outside the state-owned protected area system. As they are small fragments and located in the neighbourhood of human settlements, towns, and cities, they are likely to be affected by urbanization. We studied the effect of urbanization on the ecosystem health of sacred groves of Kerala using litterdwelling ants as the indicator taxa. Ants were pitfalltrapped (10-12 traps/sacred grove) from three rural and two urban sacred groves, and identified to species. Overall, 1,119 ants of 32 species and 6 subfamilies (Aenictinae, Dolichoderinae, Ectatomminae, Formicinae, Myrmicinae and Ponerinae) were collected. This corresponds to 76.54% of the estimated species richness. Urbanization had little impact on the species diversity of ants. Abundance was remarkably high in urban sacred groves, mainly due to higher abundance of generalist and invasive species. The effect of urbanization was indicated by different ant assemblages. Rural sacred groves had nine species and three subfamilies exclusive to them as against the five exclusive species of urban sacred groves. Urban sacred groves were characterized by high abundance of Anoplolepis gracilipes, a globally important invasive species. Sacred groves were clustered based on the rural-urban gradient as hypothesized by the study. [ABSTRACT FROM AUTHOR]

Thriving populations of invasive species often decline, but the mechanisms behind such declines are rarely elucidated. The microbial community living within insects can have significant impacts on host health and population dynamics and may be one such mechanism. Here, we use Illumina RNAseq and 16S amplicon sequencing to compare the bacterial communities, and investigate the presence of viruses, in queens of the invasive yellow crazy ant, Anoplolepis gracilipes, from populations in various stages of decline or expansion in Australia. Black queen cell virus and sequences with homology to the Dicistroviridae family of viruses were detected in queens from declining ant populations. This is the first instance of sequences with homology to a virus being found in A. gracilipes and may indicate a new virus. The overall bacterial communities were not statistically different between the population types and a number of potential mutualists were discovered. Several putative pathogens were also detected, including Candidatus Rhabdochlamydia, the entomopathogen Serratia marcescens and the reproductive parasite Candidatus Cardinium. These taxa are known to significantly affect host biology in other organisms. Our survey has identified several candidates that may be responsible for population declines of this invasive ant, and therefore may have potential as biological control agents. [ABSTRACT FROM AUTHOR]

Anoplolepis gracilipes is an invasive species that is a major threat to native ecosystems worldwide. It has been listed as one of the top 100 worst invasive species in the world and is well known for its negative impact on native arthropods and some vertebrates. This study aimed to confirm the presence or absence of A. gracilipes in some major South African harbours. We did so by surveying four harbours in the Western Cape and KwaZulu-Natal provinces, using pitfall trapping, yellow pan traps, and baiting. In addition, ant collections from Iziko Museums of South Africa (Cape Town, South Africa), University of KwaZulu-Natal (Pietermaritzburg campus, South Africa), Iimbovane Outreach Project (Stellenbosch University, South Africa), and AfriBugs CC (Pretoria, South Africa) were examined for specimens of A. gracilipes . The invasive species A. gracilipes was not detected from any of the sampled harbours during this study, nor in the main ant collections in South Africa. The only, and potentially erroneous published record of A. gracilipes in South Africa, is from Durban harbour and subsequent possibly erroneous citizen science observations are from other coastal sites such as Gansbaai, Knysna, Table Bay, and Kalk Bay. This is a positive outcome for conservation authorities as this species is highly invasive and, if introduced, will likely outcompete native fauna and result in ecosystem collapse. Although A. gracilipes was not detected in the samples from this study, early detection and eradication of this species should be prioritised. This can be achieved through existing pest monitoring programs at harbours, and continued border biosecurity measures., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Ndaba, Munyai, Mbanyana, van Noort and Janion-Scheepers.)

The tawny crazy ant, Nylanderia fulva (Mayr) (Hymenoptera: Formicidae), has invaded states of the U.S. including Texas, Louisiana, Mississippi, Alabama, Florida, and Georgia. Native to South America, N. fulva is considered a pest in the U.S. capable of annoying homeowners and farmers, as well as displacing native ant species. As it continues to expand its range, there is a growing need to develop novel management techniques to control the pest and prevent further spread. Current management efforts rely heavily on chemical control, but these methods have not been successful. A review of the biology, taxonomy, ecology, and distribution of N. fulva, including discussion of ecological and economic consequences of this invasive species, is presented. Options for future management are suggested focusing on biological control, including parasitoid flies in the genus Pseudacteon, the microsporidian parasite Myrmecomorba nylanderiae, and a novel polynucleotide virus as potential biological control agents. We suggest further investigation of natural enemies present in the adventive range, as well as foreign exploration undertaken in the native range including Paraguay, Brazil, and Argentina. We conclude that N. fulva may be a suitable candidate for biological control. [ABSTRACT FROM AUTHOR]

The entry of secondary invaders into, or their expansion within, native communities is contingent on the changes wrought by other (primary) invaders. When primary invaders have altered more than one property of the recipient community, standard descriptive and modeling approaches only provide a best guess of the mechanism permitting the secondary invasion. In rainforest on Christmas Island, we conducted a manipulative field experiment to determine the mechanism of invasion success for a community of land snails dominated by non-native species. The invasion of rainforest by the yellow crazy ant ( Anoplolepis gracilipes) has facilitated these land snails, either by creating enemy-free space and/or increased habitat and resources (in the form of leaf litter) through the removal of the native omnivorous-detritivorous red land crab ( Gecarcoidea natalis). We manipulated predator densities (high and low) and leaf litter (high and low) in replicated blocks of four treatment combinations at two sites. Over the course of one wet season (five months), we found that plots with high leaf litter biomass contained significantly more snails than those with low biomass, regardless of whether those plots had high or low predation pressure, at both the site where land crabs have always been abundant, and at the site where they have been absent for many years prior to the experiment. Each site was dominated by small snail species (<2 mm length), and through handling size and predation experiments we demonstrated that red crabs tend not to handle and eat snails of that size. These results suggest that secondary invasion by this community of non-native land snails is facilitated most strongly by habitat and resource augmentation, an indirect consequence of red land crab removal, and that the creation of enemy-free space is not important. By using a full-factorial experimental approach, we have confidently determined-rather than inferred-the mechanism by which primary invaders indirectly facilitate a community of secondary invaders. [ABSTRACT FROM AUTHOR]

While invasive species eradications are at the forefront of biodiversity conservation, ant eradication failures are common. We reviewed ant eradications worldwide to assess the practice and identify knowledge gaps and challenges. We documented 316 eradication campaigns targeting 11 species, with most occurring in Australia covering small areas (< 10 ha). Yellow crazy ant was targeted most frequently, while the bigheaded ant has been eradicated most often. Of the eradications with known outcomes, 144 campaigns were successful, totaling approximately 9500 ha, of which 8300 ha were from a single campaign that has since been partially re-invaded. Three active ingredients, often in combination, are most commonly used: fipronil, hydramethylnon, and juvenile hormone mimics. Active ingredient, bait, and method varied considerably with respect to species targeted, which made assessing factors of eradication success challenging. We did, however, detect effects by active ingredient, number of treatments, and method on eradication success. Implementation costs increased with treatment area, and median costs were high compared to invasive mammal eradications. Ant eradications are in a phase of increased research and development, and a logical next step for practitioners is to develop best practices. A number of research themes that seek to integrate natural history with eradication strategies and methodologies would improve the ability to eradicate ants: increasing natural history and taxonomic knowledge, increasing the efficacy of active ingredients and baits, minimizing and mitigating non-target risks, developing better tools to declare eradication success, and developing alternative eradication methodologies. Invasive ant eradications are rapidly increasing in both size and frequency, and we envisage that eradicating invasive ants will increase in focus in coming decades given the increasing dispersal and subsequent impacts. [ABSTRACT FROM AUTHOR]

Detailed assessment of scale insect (Hemiptera: Coccoidea) faunas on islands may help predict impacts of invasive ants (Hymenoptera: Formicidae) and inform options for their management, including biological control. Mutualism between scale insects and the invasive ant Anoplolepis gracilipes on Christmas Island, Indian Ocean, threatens the conservation of the island's endemic land crab fauna, alters rainforest structure and composition, and disrupts ecosystem processes. Diversity and endemism of the scale insect fauna were assessed through broad survey across rainforest, targeted search on endemic plant species, and inspection of ornamental and horticultural plants in settled areas. Emphasis was placed on honeydew-producing species that sustain ant supercolonies and detection of endemic scale insects that could be non-target species in a biological control programme for honeydew-producing scale insects. Origins of the fauna were inferred using scale insect databases and interception records at Ports-of-Entry for the United States and Korea. Twenty-eight scale insect species in seven families are identified for the island. Four honeydew-producing species, the lac scale Tachardina aurantiaca (Kerriidae) and three soft scale species (Coccidae), are abundant in rainforest and tended by ants. No endemic species were found. Compositionally, the scale insect fauna resembles that of many other tropical islands: almost all species are biogeographically widespread, host-plant generalists, and routinely intercepted in human-mediated dispersal pathways. The likely source bioregion is Sundaland where 27 of the 28 species on the island have been recorded and which has been the major pathway for movement of plant material to the island for over a century. [ABSTRACT FROM AUTHOR]

Yellow crazy ants ( Anoplolepis gracilipes) threaten invertebrates on many tropical islands, but little work has been done in continental ecosystems. We found 4.4-16.0 times more cruiser butterfly caterpillars were attacked in Australian rain forest sites with A. gracilipes than in native ant sites, and extrafloral nectar had little influence. [ABSTRACT FROM AUTHOR]

Invasive species are known to exhibit boom and bust cycles. We report population declines of one of the world's most serious ant invaders, Anoplolepis gracilipes (Smith) (yellow crazy ant) in Arnhem Land, Australia. Anoplolepis gracilipes populations are known to fluctuate, both spatially and temporally, but this is the first instance of quantitative monitoring of spatial declines of entire populations. We present before and after survey data on seven populations that have either declined substantially or disappeared completely without human intervention. Sites ranged in size from 1.8 to 15 ha. Although the mechanistic cause of these declines remains unknown, A. gracilipes populations in Arnhem Land represent a unique opportunity to investigate mechanisms by which a globally significant invader declines, which could have important implications for invasive species management worldwide. [ABSTRACT FROM AUTHOR]

A new invader, the 'tawny crazy ant', Nylanderia fulva (Hymenoptera: Formicidae; Formicinae), is displacing the red imported fire ant, Solenopsis invicta (Formicidae: Myrmicinae), in the southern U.S., likely through its superior chemical arsenal and communication. Alone, formic acid is unattractive, but this venom (= poison) acid powerfully synergizes attraction of tawny crazy ants to volatiles from the Dufour's gland secretion of N. fulva workers, including the two major components, undecane and 2-tridecanone. The unexpected pheromonal synergism between the Dufour's gland and the venom gland appears to be another key factor, in addition to previously known defensive and detoxification semiochemical features, for the successful invasion and domination of N. fulva in the southern U.S. This synergism is an efficient mechanism enabling N. fulva workers to outcompete Solenopsis and other ant species for food and territory. From a practical standpoint, judicious point-source release formulation of tawny crazy ant volatiles may be pivotal for enhanced attract-and-kill management of this pest. [ABSTRACT FROM AUTHOR]

Mutualism between invaders may alter a key characteristic of the recipient community, leading to the entry or in situ release of other exotic species. We considered whether mutualism between invasive yellow crazy ant Anoplolepis gracilipes and exotic honeydew-producing scale insects indirectly facilitated land snails (exotic and native) via the removal of a native omnivore, the red land crab Gecarcoidea natalis. In plateau rainforest on Christmas Island, Indian Ocean, the land snail community was surveyed at 28 sites representing four forest states that differed in the density of red crabs, the abundance of yellow crazy ants and management history. One-way ANOVAs and multivariate analyses were used to determine differences in land snail species abundance and composition between forest states. Sample-based rarefaction was used to determine differences in species richness. The removal of the red land crab by supercolonies of yellow crazy ants was associated with a significant increase in the abundance of both invasive (14 species) and native (four species) land snails. Compositional differences in the land snail community were driven most strongly by the significantly greater abundance of a few common species in forest states devoid of red crabs. In forest where the crab population had recovered following management for ants, the land snail assemblage did not differ from intact, uninvaded forest. The land snail community was dominated by exotic species that can coexist alongside red crabs in rainforest uninvaded by exotic ants and scale insects. However, the ant-scale mutualism significantly increased land snail abundance and altered their composition indirectly though the alteration of the recipient community. We suggest these constitute 'population-release' secondary invasion in which the impacts of previously successful invaders facilitate a significant increase in abundance of other exotic species already established at low density within the community. Understanding facilitative interactions between invaders and indirect consequences of impacts will provide invaluable insights for conservation in heavily invaded ecosystems. [ABSTRACT FROM AUTHOR]

Dispersal can be a crucial factor affecting fitness in insects. We conducted a series of experiments and observations with the aim of determining the dispersal mode of the African root and tuber scale Stictococcus vayssierei, a pest on cassava in the Congo Basin. We monitored the main options of dispersal that occurred in scale insects: wandering of first-instar nymphs (crawlers), active dispersal by ant workers, phoresis on colony-founding queen ants, and passive dispersal by wind. Results showed that A. tenella workers are actively involved in the transport and dissemination of scale crawlers. When ants were excluded, crawlers could move by themselves for a short distance to find the host plant. In the presence of ants, crawlers were transported by ant workers for longer distance across the bridge and established on scale-free plants. Scales transport increased with the duration of the experiment and ant density. Neither a case of phoresis nor dispersal by wind was recorded, suggesting that passive dispersal is rare. These results outline the active role of A. tenella workers in the dispersal of immature stages of S. vayssierei in Southern Cameroon and have implication in the management of the scale on cassava. [ABSTRACT FROM AUTHOR]

The lack of biological knowledge of many invasive species remains as one of the greatest impediments to their management. Here I detail targeted research into the biology of the yellow crazy ant Anoplolepis gracilipes within northern Australia and detail how such knowledge can be used to improve the management outcomes for this species. I quantified nest location and density in three habitats, worker activity over 24 h, infestation expansion rate, seasonal variation of worker abundance and the timing of production of sexuals. Nests were predominantly (up to 68%) located at the bases of large trees, indicating that search efforts should focus around tree bases. Nest density was one nest per 22, 7.1 and 6.3 m2 in the three habitats, respectively. These data form the baselines for quantifying treatment efficacy and set sampling densities for post-treatment assessments. Most (60%) nests were underground, predominantly (89%) occurring in an open area rather than underneath a rock or log. Some seasonality was evident for nests within leaf litter, with most (83%) occurring during the ‘wet season’ (October–March). Of the underground nests, most were shallow, with 44% being less than 10 cm deep, and 67% being less than 20 cm deep. Such nest location and density information serves many management purposes, for improving detection, mapping and post-treatment assessments, and also provided strong evidence that carbohydrate supply was a major driver of A. gracilipes populations. Just over half of the nests (56%) contained queens. Of the 62 underground nests containing queens, most queens (80%) were located at the deepest chamber. When queens were present, most often (38%) only one queen was present, the most being 16. Queen number per nest was the lowest in July and August just prior to the emergence of virgin queens in September, with queen numbers then remaining steadily high until April. Nothing is known for any ant species about how the queen number per nest/colony affects treatment efficacy, but further research would no doubt yield important breakthroughs for treating ants. Activity occurred predominantly nocturnally, ceasing during mid-day. These activity data determined the critical threshold above which work must be conducted to be considered reliable, and also suggests that treatments are best applied in the afternoon. Total brood production peaked in February and was the lowest around August and September. These abundance data form the baselines for quantifying treatment efficacy, and may have implications for treatment efficacy. Males were found every month, predominantly between August and November. Queen pupae were found in September. The reproductive timing of sexuals determines the treatment schedule. Targeted, site-specific research such as that described here should be an integral part of any eradication program for invasive species to design knowledge-based treatment protocols and determine assessment benchmarks. [ABSTRACT FROM PUBLISHER]

Large supercolonies of the yellow crazy ant (YCA) (Anoplolepis gracilipes) on Christmas Island (Indian Ocean) have had a major impact on the land crabs on the island, and an aerial baiting programme using Fipronil™ was trialed in 2002 to reduce YCA populations. To assess the potential for non-target impacts of this baiting programme, canopy-dwelling arthropods and selected vertebrates were sampled in four forest treatments: uninfested by YCA; infested but aerially baited several days earlier; infested but hand-baited 12-24 months previously; and, infested but untreated. Canopy arthropods from the lower canopy of five species of tree were sampled immediately after aerial baiting to determine the abundance and diversity of the arthropod fauna in infested and uninfested areas and the potential impact of the insecticide on the arthropod fauna. Relative abundances of terrestrial, diurnal bird species and the nocturnal Christmas Island gecko were estimated at replicate sites within the four treatments in September 2002 and April 2003 to detect the potential for immediate and medium-term effects of the baiting programme on habitat use. Non-baited infested sites and those that had recently been aerially baited showed significantly elevated levels of both YCA and scale insects in the canopy, and the relative abundances of these two taxa were highly correlated. After counts of YCA and scale insects had been removed, no significant differences in the overall abundance of arthropods or the number of orders encountered could be detected across the four treatments. Estimates of relative abundance of vertebrates immediately after baiting indicated that the only sampled species to respond to Fipronil™ was the Christmas Island white-eye, whose abundance was lower in non-baited control areas than in uninfested sites, or aerially baited sites with supercolonies of YCA. The Christmas Island imperial pigeon exhibited a response to baiting when sampled eight months after the initial baiting. The abundance of this species was significantly reduced in the aerially baited sites compared with that in uninfested sites, and overall abundance of this species declined between 2002 and 2003. Although our samples and counts were small, we conclude that, with the exception of reductions in abundance in the imperial pigeon, the immediate to medium-term impacts of the aerial baiting strategy on vertebrates and immediate impact on canopy arthropods were minimal and that, given the importance of control of YCA for the conservation of terrestrial fauna, such baiting programmes should be supported. [ABSTRACT FROM AUTHOR]

The timing and duration of sexual brood production in ants can affect their rate of spread and colony growth. Because protein is key to larval growth, queen survival and fecundity, macronutrient collection by foraging workers is expected to favour protein prior to and throughout gyne production. However, food preference driven by the production of gynes may be overridden by a preference associated with worker production, especially if investment in workers vastly outweighs that of sexual brood and workers are produced on different schedules. Food preferences alone may not indicate the availability of that food type in the environment. On Christmas Island, Indian Ocean, sexual brood of the invasive Yellow Crazy Ant, A noplolepis gracilipes ( Smith, 1857), was produced annually during a single period associated with the onset of the wet season. However, workers were produced continuously throughout the year and colony investment to worker production measured by the standing biomass of eggs, larvae and pupae, typically exceeded 98%. High, aseasonal investment in worker production, together with aseasonal worker activity, would suggest that there should be no seasonal preference shown by workers at food stations containing both protein and carbohydrate. However, workers showed a preference for one food type over another on 46 of 61 occasions at one site and on 31 of 41 occasions at another. When a preference was shown, it was predominantly for protein-rich food during the dry season and almost always for carbohydrate at the onset and during the wet season. We suggest that these preferences reflect seasonal shortages in key resources when invertebrates (protein-rich) are scarce during the dry season and honeydew from scale insects (carbohydrate) is depleted by rain during the wet season. On Christmas Island, timing and duration of the dry season preference for protein has been exploited by the control program for A . gracilipes supercolonies, which deploys a toxin in a proteinaceous bait matrix during dry periods. [ABSTRACT FROM AUTHOR]

The red crab, Gecarcoidea natalis, is endemic to Christmas Island in the Indian Ocean and largely responsible for shaping the unique ecosystem found throughout the island's rainforests. However, the introduction and establishment of supercolonies of the highly invasive yellow crazy ant, Anoplolepis gracilipes, has decimated red crab numbers over the last several decades. This poses a significant risk to the future conservation of G. natalis and consequently threatens the integrity of the unique island ecosystem. Here we undertook a population genetic analysis of G. natalis using a combination of 11 microsatellite markers and sequencing of the mitochondrial cytochrome oxidase subunit I gene from samples collected on Christmas Island as well as a single location from North Keeling Island (located approximately 900 km west of Christmas Island). The genetic results indicate that G. natalis is a single panmictic population on Christmas Island, with no spatial genetic structure or restricted gene flow apparent between sampled locations. Further, G. natalis from North Keeling Island are not genetically distinct and are recent immigrants from Christmas Island. The effective population size of G. natalis has likely remained large and stable on Christmas Island throughout its evolutionary history with relatively moderate to high levels of genetic diversity in microsatellite loci and mitochondrial haplotypes assessed in this study. For management purposes G. natalis can be considered a single panmictic population, which should simplify conservation efforts for the genetic management of this iconic island species. [ABSTRACT FROM AUTHOR]

The mature palm forest of the Vallée de Mai, a UNESCO World Heritage Site, on the Seychelles island of Praslin, is a unique ecosystem containing many endemic species, including the iconic coco de mer palm Lodoicea maldivica. In 2009, the invasive yellow crazy ant Anoplolepis gracilipes was recorded for the first time within the palm forest, raising concern about its potential impacts on the endemic fauna. This research aimed to: (1) assess the current distribution and spread of A. gracilipes within the palm forest; (2) identify environmental variables that are linked to A. gracilipes distribution; and (3) compare endemic species richness and abundance in A. gracilipes invaded and uninvaded areas. Anoplolepis gracilipes was confined to the north-east of the site and remained almost stationary between April 2010 and December 2012, with isolated outbreaks into the forest. Infested areas had significantly higher temperature and humidity and lower canopy cover. Abundance and species richness of the endemic arboreal fauna were lower in the A. gracilipes invaded area. Molluscs were absent from the invaded area. The current restricted distribution of A. gracilipes in this ecosystem, combined with lower abundance of endemic fauna in the invaded area, highlight the need for further research to assess control measures and the possible role of biotic resistance to the invasion of the palm forest by A. gracilipes. [ABSTRACT FROM AUTHOR]